| Objective: To observe protection effects of myocardial IPC and IPO against ischemia-reperfusion, then to study the possible mechanism and adding effects of each; And the relationship was studied between the protection effects of IPC ,IPO and PKCα.Methods: 50 male Sprague-dawley rats ,weight 250-300 g, were randomly divided into five groups : Group NC(normal control group, n=10) : the chest of rats opened, LAD(left anterior descending) was thread but not occluded; Group IR ( ischemia reperfusion group, n=10 ) : the rat hearts were subjected to 40 minutes of LAD occlusion and 120 minutes of reperfusion; Group IPC(preconditioning group, n=10 ) : with 3 cycles of 5 minutes of ischemia, each followed by 10 minutes of reperfusion, then followed IR group; Group IPO ( postconditioning group, n=10 ) : with 40 minutes ischemia followed by 120 minutes reperfusion, reperfusion was initiated for 30 seconds of reperfusion followed by 30 seconds of reocclusion, repeated for 3 cycles(3 minutes total intervention); Group IPC+IPO ( preconditioning + postconditioning group, n=10 ) : with protocol similar to that of IPO group except for 3 round 15 minutes ischemic preconditioning applied before 40 minutes ischemia. All rats were nothing by mouth 3 hours before anesthesia ,incision of trachea and ventilatory support of breathing machine, median incision of manitruncus. All animals were given heparine 500u/kg before the first time occlusion of LAD in order to preventing thrombosis. Observed indicatrix:①CK-MB: 1ml blood sample collected from right auricle before LAD was occluded, 30 minutes,60 minutes,120 minutes of reperfusion, CK-MB was observed at automatic biochemistry analyser.②The area of myocardial infarction: after experiment harvesting the heart, occluded LAD and perfusing 0.5﹪Even's blue dye through arota, to part the blue-stained area and non blue-stained area ,the non blue-stained area was frozen and sliced ,then it was dyed by TTC. At last it was weighed with electronic balance ,computing the data.③SOD,MDA: after 120 minutes reperfusion, the abdominal cavity was opened ,2-4 ml blood sample was collected from cava, 4500r/min. efference and -20℃conservation.④PKCα: the specimen were immobilized by 4﹪paraform and dyed by immuno-histochemistry.⑤The rate of arrhythmia: ECG of rats were observed and the rate of arrhythmia were analyzed after reperfusion.⑥The index of morphology: After reperfusion ,suitable myocardial specimen was harvested and fixed, then it was observed under light microscope and electronic microscope.Results:①The results showed that there was no distinction of CK-MB basal level in every group. The CK-MB level was stepping up along with the reperfusion time 30 minutes,60 minutes,120 minutes in IR group,IPC group,IPO group and IPC+IPO group. So it indicates that every group exist reperfusion injury effect. But the CK-MB level of IPC,IPO and IPC+IPO group was lower than IR group at each time spot, so it hints that IPC,IPO and IPC+IPO could relieve ischemic reperfusion injury. However, CK-MB in Group IPC, IPO and IPC+IPO had no difference.②The infarction area in IPC,IPO and IPC + IPO group was lower than that in reperfusion group(p<0.05) , but there was no statistical signification in the post three groups.③Biochemistry index showed that SOD was higher in group IPC ( 88.95±7.73 ),group IPO (85.36±7.25 ) and group IPC+IPO (84.69±11.68)than that in group IR (65.19±7.73 ),(P<0.05 ) moreover, MDA of group IR was higher than group IPC, IPO and IPC+IPO(P<0.05).④The rate of PKCαabout ventricular myocardium in group IPC (66.6±7.85% ),group IPO (61.41±6.95%) and group IPC+IPO (61.97±2.80%)was higher than that of in group IR (9.42±1.35%),group NC(9.29±1.16%).⑤The rate of arrhythmia was 0 in control group,90% in IR group,10% in IPC group,20% in IPO group and 20% in IPC+IPO group. The rate of arrhythmia in reperfusion group was significantly higher than that in later three group (P<0.00714), however, there was no difference in the later three groups(P=1.000).⑥There was great variety of tissue appearance between IR group and IPC,IPO,IPC+IPO group; But there was alike or similar morphology change in IPC,IPO and IPC+IPO group.Conclusion: 1 Reperfusion may destroy myocardial cells significantly, the results was cell necrosis and arrhythmia rate adding. 2 ischemic preconditioning, ischemic postconditioning and ischemic preconditioning+ ischemic postconditioning could release reperfusion damage and deflate infarction size, so it can protect myocardium. 3 PKCαparticipates the process of ischemic preconditioning, ischemic postconditioning and ischemic preconditioning+ ischemic postconditioning, but there were no adding effects in ischemic preconditioning and ischemic postconditioning.
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